This invention relates generally to automatic transmission systems of motor vehicles, and more particularly automobiles. More specifically, this invention pertains to the coupling of an engine to a transmission that is unrelated to the engine.
Most automobiles manufactured today include automatic transmissions that have replaced the traditional manual transmissions. An automatic transmission typically includes a torque converter in place of the clutch of the manual transmission. A torque converter is a type of fluid coupling between the engine and the transmission to allow the engine to run somewhat independent of the transmission. The torque converter enables the engine to continue to operate while the engine idles or the automobile is stopped.
A flexplate, also occasionally referred to as a flywheel, connects the torque converter to an engine crankshaft. A typical coupling arrangement of a flexplate 14, engine crankshaft 12 and torque converter 10 is shown in FIG. 1A. The flexplate 14 is placed on the end of the crankshaft 12 whereby a hub 15 on the end of the crankshaft 12 extends through a centered boring on the flexplate 14. Flexplate 14 is bolted to the crankshaft 12 using bolts 21 threaded into apertures on a flange 22 disposed on the end of the crankshaft 12. The torque converter 10 has a hub 16 that is inserted into the hub 15 on the crankshaft 12, and the torque converter 10 is bolted to the flexplate 14. The flexplate 14 is secured to both the crankshaft 12 and the torque converter 10 so the torque converter 10 rotates at substantially the same rate of speed as the flexplate and crankshaft. In addition, a gear section, or ring gear on the flexplate engages a starter to initiate rotation of the flexplate when the engine is started.
In racing applications or after-market modifications of automobiles, an engine produced by a particular manufacturer is often times coupled to a transmission produced by another manufacturer, or an engine and transmission are matched whereby the transmission cannot be directly coupled to the engine. In such circumstances, the components, namely the torque converter, crankshaft and/or flexplate, do not match one another for purposes of installation or operation. The traditional methods of coupling the transmission to the engine include providing a flexplate from either the engine or transmission. In addition, one or more adaptor components such as spacers, mounting hubs, tubular standoffs etc., are provided, and sometimes original parts are re-tooled in order to mate the transmission to the engine.
An example of a prior art adaptor assembly for coupling a transmission to an engine is illustrated in FIG. 1B. In this example, a flexplate 14 from the engine 13 and various adaptors or spacers couple a transmission 11 and torque converter 10 to the engine 13 and engine crankshaft 12. The crankshaft 12 has a pilot hub 15 and flange 22 for respectively aligning and mounting the flexplate 14 to the end of the crankshaft 12. The torque converter 10 and transmission 11 are unrelated to the engine 13 and engine crankshaft 12 as they are produced from a manufacturer other than the manufacturer of the engine 13. Accordingly, the torque converter 10 cannot be mated with the engine crankshaft 12 or secured to the flexplate 14 without adaptors. In this example, the torque converter hub 16 is too small in diameter to properly mate with the hub 15 on the crankshaft 12.
Accordingly, a hub adaptor 17 is mounted to the flexplate 14 and crankshaft 12 using crankshaft bolts 17A, for receiving the torque converter 10. In some adaptor kits, the adaptor hub 17 may be purchased in an assembled fashion, whereby the hub adaptor 17 is already bolted or welded to the flexplate 14. The hub adaptor 17 displaces the transmission 11 and torque converter 10 aft of the vehicle in which the transmission 11 and engine 13 will be mounted. Therefore, spacers 20A, 20B and bolts 21A, 21B must be used to respectively mount the torque converter 10 to the flexplate 14 and the transmission bell housing 18 to the engine 13. Moreover, adaptor 20B between the bell housing 18 and engine 13 accounts for the misalignment of apertures on the bell housing 18 with respect to apertures on the engine 13.
The adaptor systems or kits, as shown in FIG. 1 and described above, have various components that must be properly aligned and bolted together. Assembling such a system can be time consuming and difficult. The components can be lost during assembly or misaligned when assembled. In as much as the components are bolted to one another or to the transmission and engines, as the automobile engine runs the bolts often loosen and sometimes break.
Alignment, true running, and squareness of the engine/transmission assembly are important in production vehicles; however, as the performance demands increase, accuracy becomes increasingly critical. Heavy loads and higher engine speeds exaggerate all problems associated with alignment issues. Unchecked, these problems result in failed engines and transmissions due to excessive forces created during operation.
Each part of a motor vehicle engine and transmission must have an allowable machining tolerance on its size. When multiple parts are assembled together, all of the sizes, misalignments, and non-squareness tolerances (errors) start to add up. Even with precision machining and assembly, more parts translate to more opportunities for more misalignments.
To further aggravate the problem, whenever parts are bolted together, additional clearances must be designed in to provide clearance for the fasteners to fit. When more parts are bolted together individually, or when sandwiched between a single set of bolts, each bolt joint becomes susceptible to movement between the faces of the bolted parts due to vibration, cyclic loading, or even temperature variations. Once parts start to chafe or the bolt tightness begins to loosen, the bolt faces of the parts rapidly begin to wear and become even looser allowing misalignment or even wobbling and unbalance. The whole system can quickly and catastrophically fail at that point.
In an attempt to solve bolting/clamping problems with multiple part connections, welding is sometimes employed. Welding creates it own set of characteristic problems. The two most common problems are distortion and weld induced residual stresses. Since welding is the act of melting metal in multiple parts together, as the melted areas start to cool, they shrink and distort which warps, twists, and bends the previously straight parts making squared and aligned finished products virtually impossible. The second problem is that welding changes the metallurgical properties of the parts and differing cooling rates of the parts create residual stresses, which limit the amount of load that can be applied to the parts before they break.